Investigation of the bearing capacity of pyramidal piles

Abstract

1. Pyramidal piles work most effectively not in the zone of their maximum cross section but beginning with a depth of 0.5–1 m from the ground surface, and therefore it is economically advisable to provide for a prismatic part in the upper end of the pyramidal pile. 2. An increase of bearing capacity of the pyramidal pile in comparison with prismatic is achieved as a consequence of the occurrence in the soil during their penetration of a passive earth pressure\(\sigma _{pa_2 } \) which provides additional skin friction. 3. The passive earth pressure and consequently the additional resistance of the pyramidal pile due to the arising thrust do not depend on depth, and within the length of the pile they vary inversely proportional to the size of the side of the pile cross section. 4. The additional skin friction of the pyramidal pile is greater, the greater the modulus of deformation of the soil and its angle of internal friction. 5. It is most advisable to use pyramidal piles at sites composed of soils homogeneous depthwise or in the case of a decrease of deformation and strength characteristics with depth. The maximum effect from the use of pyramidal piles can be obtained only in soils having relatively high moduli of deformation and angles of internal frictions, i.e., in sands, loamy sands, loams with a small plasticity index, loesslike loams, and loess. Pyramidal piles are not effective in clays having a high plasticity, whose strength properties depend mainly on cohesion.